Dynamic characteristics of bare conductors.
Loading...
Date
2011
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
The dynamic characteristic of transmission line conductors is very important in designing and
constructing a new line or upgrading an existing one. This concept is an impediment to line
design and construction because it normally determines the tension at which the line is strung
and this in respect affects the tower height and the span length. Investigations into the
phenomenon of mechanical oscillation of power line conductors have been extensively looked
into by many researchers using concepts from mechanics and aerodynamics to try and predict the
conductor dynamic behaviour. Findings have shown that precise prediction of conductor windinduced
vibration is very difficult i.e. non-linearity.
Over the years, various analytical models have been developed by researchers to try and predict
the mechanical vibration of transmission line conductors. The first part of this dissertation
considers the analysis of the model describing the transverse vibration of a conductor as a long,
slender, simply supported beam, isotropic in nature and subjected to a concentrated force. The
solution of this beam equation was used to obtain the conductor natural frequencies and mode
shapes. Conductor self-damping was obtained by the introduction of both external and internal
damping models into the equation of motion for the beam.
Next, also using the same beam concept was the application of the finite element method (FEM)
for the dynamic analysis of transmission line conductors. A finite element formulation was done
to present a weak form of the problem; Galerkin‟s method was then applied to derive the
governing equations for the finite element. Assembly of these finite element equations, the
equation of motion for the transverse vibration of the conductor is obtained. A one dimensional
finite element simulation was done using ABAQUS software to simulate its transverse
displacement. The eigenvalues and natural frequencies for the conductors were calculated at
three different tensions for two different conductors. The damping behaviour of the conductors
was evaluated using the proportional damping (Rayleigh damping) model. The results obtained
were then compared with the results from the analytical model and the comparison showed a
very good agreement.
An electrical equivalent for the conductor was developed based on the concept of mechanicalelectrical
analogy, using the discrete simply supported beam model. The developed electrical
equivalent circuit was then used to formulate the transfer function for the conductor. Matlab
software was used to simulate the free response of the developed transfer function.
Finally, the experimental study was conducted to validate both the analytical model and the
FEM. Tests were done on a single span conductor using two testing methods i.e. free and force
vibration. The test results are valid only for Aeolian vibration. From the test results the
conductor‟s natural frequencies and damping were determined. The experimental results, as
compared with the analytical results were used to validate the finite element simulation results
obtained from the ABAQUS simulation.
Description
Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2011.
Keywords
Electric conductors., Electric lines., Electric power transmission., Theses--Electrical engineering.